Sunday, January 5, 2020

Round Pegs and Square Holes: Proper Planting

I've been seeing some advice making the rounds lately from many sources via social media. Plant your trees in square holes to make them grow healthier and faster. This info is being re-blogged and re-shared over and over and I'm seeing a lot of discussion about it. There may not be anything specifically WRONG with doing so, but I highly doubt it's beneficial. I planted some things in square-ish holes this fall; not because I think it's beneficial, but because it was faster to just strip a couple sections of sod off and not worry about rounding the hole. I had a lot of plants to get in the ground and time was of the essence.

What I didn't take shortcuts on was proper preparation of plants for planting. This meant root-washing or root-shaving. Because of the circumstances of the last several years, many of my plants have been potted for an extended period. Some as long as 10 years. So many have dense root systems and girdling roots. For healthy, long-term growth it's important that the root system can grow properly. Roots need to be straightened, and even pruned if necessary. Many of the plants you purchase at nurseries have been in containers for extended periods of time. They may have several layers of girdling roots and they may be planted too deeply. Rootwashing is the best way to fix these problems.

This Hydrangea arborescens was in this pot for 3 years. I use a hose end sprayer set to jet to wash off as much of the loose soil as I could.

After washing, I removed large girdling roots that were on the interior of the root mass, hidden by the soil.

This Abies concolor 'Compacta' wasn't rootwashed before being planted in the last garden, and then spent 3 years in a pot. I completely root washed it (sadly I didn't get a final picture that turned out well) and straightened most of the roots. I did have to prune a few of the worst girdling roots out.

 Even herbaceous plants will benefit from root washing and correction. Look at the girdling roots on this young perennial! They were easily straightened during planting.

This Hosta 'Bridal Falls' has a wonderful root system. A quick root wash and the roots were easily straightened out. This is how most perennials should look before you backfill the planting hole.

I mentioned root shaving as well. This is where you shave off an inch or so all the way around the root ball to eliminate outer circling roots. This is a good method for plants with dense fibrous root masses but no larger girdling roots. I did this for some azalea cultivars and a few other things that just don't easily form large support roots. Doing so ensures that the roots will grow outwards into the surrounding soil instead of staying in the shape of a pot. 

Speaking of soil, what about soil prep? Elsewhere on this blog, I talk about amending soil. Mostly I no longer recommend it. The best thing for plants is to skip amending soil with peat, compost, or other organic additives. Native soil is your best option. There are some exceptions to this, like when you create raised beds. If you're planting something that needs better drainage (I like Primula for instance) consider creating a raised bed with an appropriate soil mix for them. Some organic amendments work well for mulches, and mulch is something I strongly recommend.

How about fertilizer? Most in-ground plants need a lot less fertilizer than we give them. A soil test is essential to making decisions about fertilizer. And I don't mean a store-bought test you do at home. Contact your local university extension office for a proper soil test. 

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